Fermi-LAT detection of enhanced gamma-ray activity from the FSRQ B2 1324+22
ATel #17325; G. La Mura (INAF - Astronomical Observatory of Cagliari), on behalf of the Fermi Large Area Telescope Collaboration
on 8 Aug 2025; 19:35 UT
Credential Certification: Giovanni La Mura (giovanni.lamura@inaf.it)
Subjects: Gamma Ray, >GeV, AGN, Blazar, Quasar
The Large Area Telescope (LAT), one of the two instruments on the Fermi Gamma-ray Space Telescope, has observed enhanced gamma-ray activity from a source positionally consistent with the flat-spectrum radio quasar B2 1324+22, also known as 4FGL J1326.9+2210 (Abdollahi et al. 2022, ApJS, 260, 53), with coordinates R.A. = 201.75359 deg, Dec. = +22.18060 deg (J2000; Truebenbach et al. 2017, ApJS, 233, 3), and redshift z = 1.398 (Albareti et al. 2017, ApJS, 233, 25).
Preliminary analysis indicates that this source was in an elevated gamma-ray emission state on August 7, 2025, with a daily averaged gamma-ray flux (E>100MeV) of (0.5+/-0.1) X 10^-6 photons cm^-2 s^-1 (statistical uncertainty only). This corresponds to a flux increase of a factor of 20 relative to the average flux reported in the fourth data release of the fourth Fermi-LAT catalog (4FGL-DR4, Ballet et al. 2023, arXiv:2307.12546). This is the highest LAT daily flux ever observed for this source. The corresponding photon index is 2.2+/-0.2, indicating a harder spectrum than the 4FGL-DR4 value of 2.48 +/- 0.03.
Because Fermi normally operates in an all-sky scanning mode, regular gamma-ray monitoring of this source will continue. A preliminary light curve for B2 1324+22 can be accessed via the Fermi-LAT Light-Curve Repository at 4FGL J1326.9+2210. We encourage multifrequency observations of this source. For this source, the Fermi-LAT contact person is Giovanni La Mura (giovanni.lamura@inaf.it).
The Fermi-LAT is a pair conversion telescope designed to cover the energy band from 20 MeV to greater than 300 GeV. It is the product of an international collaboration between NASA and DOE in the U.S. and many scientific institutions across France, Italy, Japan and Sweden.
